diff --git a/gtk2_ardour/progress_dialog.cc b/gtk2_ardour/progress_dialog.cc
index 0cee9878e7..af3f86251c 100644
--- a/gtk2_ardour/progress_dialog.cc
+++ b/gtk2_ardour/progress_dialog.cc
@@ -129,20 +129,36 @@ ProgressDialog::add_progress_step ()
 void
 ProgressDialog::show_pd ()
 {
-    WavesDialog::show ();
+    Gtkmm2ext::UI::instance()->call_slot (invalidator (*this), boost::bind (&ProgressDialog::show_pd_in_gui_thread , this));
+}
+
+void
+ProgressDialog::show_pd_in_gui_thread ()
+{
+   WavesDialog::show ();
     /* Make sure the progress dialog is drawn */
-    Glib::MainContext::get_default()->iteration (false);
+    while (Glib::MainContext::get_default()->iteration (false)) {
+        /* do nothing */
+    }
 }
 
 void
 ProgressDialog::hide_pd ()
 {
-    Glib::MainContext::get_default()->iteration (false);
+   Gtkmm2ext::UI::instance()->call_slot (invalidator (*this), boost::bind (&ProgressDialog::hide_pd_in_gui_thread , this)); 
+}
 
+void
+ProgressDialog::hide_pd_in_gui_thread ()
+{
+    while (Glib::MainContext::get_default()->iteration (false)) {
+        /* do nothing */
+    }
     set_progress (0);
     WavesDialog::hide ();
 }
 
+
 void
 ProgressDialog::show_cancel_button ()
 {
diff --git a/gtk2_ardour/progress_dialog.h b/gtk2_ardour/progress_dialog.h
index df2c8e14cc..bf2144a421 100644
--- a/gtk2_ardour/progress_dialog.h
+++ b/gtk2_ardour/progress_dialog.h
@@ -58,6 +58,8 @@ private:
                const std::string& top_message,
                const std::string& progress_message,
                const std::string& bottom_message);
+	void show_pd_in_gui_thread ();
+	void hide_pd_in_gui_thread ();
     void set_progress_in_gui_thread (float);
     Gtk::Label& _top_label;
     Gtk::Label& _bottom_label;